[TUHS] Serial Interfaces (was ^T and Top)
Dave Horsfall
dave at horsfall.org
Thu May 31 08:46:46 AEST 2018
On Wed, 30 May 2018, Clem Cole wrote:
> Right - you have to escape things and it is a real mess. I have seen
> some of the SI/SO/DLE stuff in mechanical systems like ticker tape. I
> never saw a real 8-bit interface try to do it and succeed -- its messy
> and suspect when data overruns occurs all hell break loose. By the time
> of 8 bits and speed of 9.6K protocol's like UUCP, or IP over serial did
> not even bother. I suspect in the old 5-bit baudot code times, it was
> more popular to get a larger character set, but the speeds were much
> slower (and the UART not yet invented by Gordon Bell).
Actually, the closest I've seen DLE being used was in SLIP and PPP; if you
needed to send a Frame End then it was escaped with (I think) 0xFF, and that
in turn was escaped. All it took was a finite state machine... Of course,
those links used RTS/CTS, but you had to flag the end of a frame (packet)
somehow.
-- Dave
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